Calibration of resistance factors for drilled shafts for the new FHWA design method : [tech summary].

Details

• Creators:
  Abu-Farsakh, Murad
• Corporate Creators:
  Louisiana Transportation Research Center
• Corporate Contributors:
  Louisiana State University (Baton Rouge, La.). Department of Civil and Environmental Engineering ; Louisiana. Dept. of Transportation and Development
• Subject/TRT Terms:
  • Load factor
  • Design load
  • Foundations
  • Piles (Supports)
  • Calibration
  • Boreholes
  • Statistical analysis
  • Load factor design
  • Foundations
  • Piling (Civil engineering)
  More +
• Publication/ Report Number:
  LTRC Report 495
• Resource Type:
  Tech Report
• Geographical Coverage:
  Louisiana
• Corporate Publisher:
  Louisiana Transportation Research Center
• Abstract:
  The load and resistance factor design (LRFD) has been increasingly used and has become mandatory for the design of all bridge projects funded by the Federal ; Highway Administration (FHWA). Compared to the allowable stress design (ASD) method, LRFD can achieve a compatible reliability between the bridge ; superstructure and substructure. The uncertainties of load and resistance are quantifi ed separately and reasonably incorporated into the design process. ; Therefore, this reliability-based design approach will generally produce a more effi cient and consistent design than the traditional ASD factor of safety approach. ; To achieve these goals, many researchers have been working to develop a reasonable way to implement the LRFD method in bridge substructure design and to ; determine appropriate resistance factors for diff erent regional soil conditions. Although the American Association of State Highway and Transportation Officials ; (AASHTO) LRFD specifi cations were approved for use in 1994, the implementation of these specifi cations for bridge design has been slow. The resistance ; factors (ɸ) proposed in the specifi cations were derived from ASD safety factors to maintain a consistent level of reliability with past practices. As a result, little ; improvement has been made toward a more efficient design. One outstanding problem with the resistance factor calibration is the lack of a good database. In ; the latest edition of the AASHTO specifi cations, a signifi cant number of resistance factors in the foundation design were still selected based on the calibration. ; Several research efforts have been carried out to calibrate the resistance factors for drilled shafts from case histories available nationally. Currently, AASHTO ; specifi cations recommend using total resistance factors (ɸ) for single drilled shafts in an axial compression range from ; 0.40 to 0.60 at a reliability index (β) of 3.0, depending on different soil conditions. These factors were calibrated based ; on drilled shaft databases that were collected from various sites that do not necessarily reflect the local soil condition ; of individual states. As a result, the resistance factors recommended by the AASHTO LRFD design code should be ; verified and recalibrated to account for local soil conditions and design experience.
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• Format:
  PDF
• Funding:
  SIO No. 3000280 ; LTRC Project No. 11-4GT
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/25681/dot_25681_DS1.pdf
• File Type:
  [PDF - 172.36 KB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha-512:acba2c189d748bff5e61c838ab2fc95dbdcbe3b0caae4069d4be0fcfdfe5124e4283fbd5edd1e5abe1e61a41e448ea285b1c1ed56fb8ac8566af749b42065201